1. Field of the Invention
The present invention relates to an active filter characteristic changeover circuit for use in a VCR (video cassette recorder), and more particularly, to a video signal active filter characteristic changeover circuit for use in a VCR having a VHF mode and a super VHS (SVHS) mode.
2. Description of the Prior Art
In an SVHS mode, since video signal over a higher frequency band can be recorded and reproduced than in a VHS mode, the passing frequency band of a luminance signal in a filter is from 0 to 5 MHz in the SVHS mode, and a frequency band wider than a frequency band of from 0 to 3 MHz used in the VHS mode is required.
In conventional VCRs, as shown in FIG. 1, two discrete filters having different characteristics are provided for the SVHS mode and the VHS mode, respectively, and these filters are changed over in response to a changeover of these modes. In FIG. 1, the numeral 2 filter for the VHS mode, represents a and the numeral 3 represents a filter for the SVHS mode. The numerals 1 and 4 represent switches provided on the input and output sides of the filters 2 and 3, respectively, and are changed over in synchronization with each other.
However, the conventional circuits where the filters are changed over in response to a changeover between the VHS and SVHS modes to change over a path of a luminance signal are disadvantageous, for example, in constructing the filters in the form of integrated circuit since two filters are required. That is, in constructing a filter in the form of integrated circuit, the filter generally occupies a large area of an integrated circuit. Therefore, if there are two filters, a larger area is occupied by the filters on a semiconductor integrated circuit chip. This makes it impossible to decrease the size and cost of the chip.
Moreover, by the conventional method where different filters are used for the VHS and SVHS modes, respectively, a problem arises that one path including one filter is offset against the other including the other filter with respect to signals passing through them.